Forthcoming changes to the 29er
Being immersed in 29ers via Asia and southern central Europe and forecasting the boat’s use in 3, 4 and 5 years down the track, I would like to propose the following changes.
Three issues are affecting the long-term use of the 29er, and those are:
#1 – the cannoning of the mast sections into each other, under ever increasing rig tensions
#2 – switching to a new 49er style gooseneck should be a foregone conclusion and is just housekeeping, we should have done this years ago, but put it off so it was done at the same time as the carbon mast which obviously isn’t going to happen anytime soon
#3 – the deterioration of the watertight seal of the scuppers particularly in the Asian environment but is also now starting to show itself in southern USA & northern Australia
#1 Cannoning of the mast joints. This is the movement of the top-mast downwards into the mid-mast and the mid-mast into the lower mast, under increasing rig tension loads, in part because the boat is being pushed harder by the latest generation of sailors and in part because of the introduction of the turnbuckles, again because the boat is now being sailed by a more determined group.
Simply, the existing array of bolts and “spreader bars” are not sufficient.
Mid-mast into lower-mast is by far the simplest, there is already a sleeve there to anchor the spreader, we just need to increase the number of M6 MT (metal-thread) bolts by 50%. Better still if we use CSK (countersunk) heads on the additional bolts as these will spread the load onto the 1.71mm wall of the lower-mast more effectively.
In detail, the internal sleeve that is used to anchor the spreader and secure the mid-mast and lower-mast together would be lifted 20 mm, and secured as it is presently. The spreader would still be attached in exactly the same way and in addition to that in-line with the bolts attaching the spreader, approx. 20mm above the spreader we would add 2 x M6 MT CSK bolts going from the lower-mast, through the mid-mast and into the sleeve. They would be approx. 10mm in length.
The top-mast into the mid-mast on closer examination is a little more complex. There are 2 movements. 1st is the securing of the existing sleeve into the FRP top-mast. Because it flexes, the existing sleeve moves inside the FRP laminate, there is nothing holding it (the sleeve) hard against the inside wall of the FRP, hence my comments above about going to a t-ball for the trapeze wires.
I have considered approximately 6 different options to secure the sleeve, and in terms of retro fitting and in terms of going forward, switching to the use of a t-ball and key plate I believe is the best solution.
By switching to a key-plate anchor, you have 4 x M5 rivets holding the alloy sleeve hard against the FRP tube. We know that 4 x M5 rivets is enough to withstand about 4 tonnes which is more than you can ever subject a 29er to. Retro fitting, the ID of a Keyplate is 8-10 mm, the hole is 8-10mm, it is accessible from the joint, it can be done easily. Even just adding 4 x M5 rivets approximating the position of a key plate above and below the existing spreader bar would dramatically alter the structural integrity of the sleeve/FRP joint.
T-balls are well known, simple, cheap, there could be even a negative (as in cheaper) cost consequence of the change.
Once you secure the sleeve into the FRP, then adding 2 x M6 MT CSK bolt, in nearly exactly the same way as I am suggesting we do at the Mid-mast/Lower-mast interface should take the structural integrity of the joint above the critical level and arrest the movement.
#2 Adoption of a 49er style gooseneck. The kids are driving the boats harder, there are tell-tale signs of stress at the front of the boom. And the biggest bug-bear of the vang shoe falling off, especially in older boats, simply goes away. 6mm pin, it’s simply “fit for purpose”!
I would also seek to use grommets for the mainsheet blocks as people are moving to lash on blocks and the grommets are far more structurally sound. They are already used on the Tasar boom which uses the 29er section and it has stopped their boom breakage problems.
Sourcing parts direct from source will also be refined. The alloy for instance could be milled at source in NZ, reducing weight, length, so enhancing logistics, and dramatically enhancing replacement options and the one-design nature of the boat. We have already done this as a test with the 49er boom, reduced rigging time by 75% with the obvious reductions in costs.
Finally, it will be my intention to use the appropriate “fastenings” where needed. If we go for T-Ball/KeyPlate trapeze then it is appropriate to use rivets. In a lot of other places, it is appropriate to use MT’s. This has to do with access (or rather lack of access) to riveters in many parts of the world.
#3 Scuppers. Recently we replaced the post moulding screw on foot-rails with moulded in foot-rails. The rationale was simple, that the screw on foot-rail was the source of many leaks, they were a source of on-going maintenance and a major cost to install and to warranty.
The resulting moulded in foot-rails do exactly the same job, but simply do it so much better.
Until early this year, we believed we had overcome all the major issues surrounding the scuppers, the switch to MMA adhesive, new mouldings, etc, gave us great hope.
No question they are better, but they are still not perfect.
In humid tropical climates, we are still getting rot quite quickly and even in LA, a 3 year old boat required complete replacement of the scuppers.
Therefore, I intend to replace the scuppers with a trench.
The similarities with the foot-rails are near identical, rather than post fitting, it’s moulded in, and the financial benefits (savings) are far greater with the trench than the post-fitted footrails.
It will do exactly the same thing. And by my calculations at near exactly the same rate.
In detail, directly under the top rudder gudgeon, we would mould a trench from the top of the transom bulkhead, down to the top of the cockpit floor. It would be approximately 60mm wide at the cockpit floor (+/-30 mm per side), growing to approximately 70-75mm wide under the top gudgeon plate (draw angle). Basically, where the World Sailing hull number plaque is presently placed. There would be suitable radiusing of the corners, etc. We would also “let in” the new alloy top rudder gudgeon (see below) so the depth of the rudder stock does not alter.
We would replace the 2mm thick SS top gudgeon plate with 6mm Alloy plate and secure it with 2 x M8 MT CSK bolts each side (this is exactly the same sort of plate that we use on the SKUD).
There would be no changes to the angle of the rudder, the rudder stock or the placement of the drain bung, as the bottom of this trench is about 50mm above the transom flange.
The result will be no rot to speak off, no leaks, nothing to work itself loose.
Longer term, considerable cost savings, as there is no 2nd fitting, there are no 2nd mouldings. The only fitting change is you screw down an alloy plate rather than a stainless plate.
These changes will be open for discussion at the LA World Championships 2017.
10 June 2017